Date Presented

Spring 5-15-2022

Document Type


Degree Name

Bachelor of Science



First Advisor

Dr. John Styrsky

Second Advisor

Dr. Jennifer Styrsky

Third Advisor

Dr. Holly Gould


Local adaptation is a common process that occurs in organisms with wide geographic ranges to maximize fitness in different environments. One specific species that has been shown to have certain locally adapted traits is Common Milkweed, Asclepias syriaca. A handful of these traits include height, stem count, number of leaves, and length and width of the leaves. The size and density of stomata, the pores underneath the leaf used for gas exchange and transpiration, may also be influenced by environmental conditions; however, this relationship has not been studied in common milkweed. In order to analyze population-level differences in the density and size of stomata in A. syriaca, a common garden experiment was used which allowed for multiple different genotypes from across the large geographic range to be planted in one specific region. The seeds were collected from 35 different locations ranging from northwest Minnesota to southern Maine and down to central Virginia. Representatives of ten different populations, from a total of 45 different mother plants with six replicates of each plant, were placed in a common garden experiment. After growth, a subset of leaves was collected to create leaf impressions which allowed analysis of stomata density and size. The underside of the leaves were coated in lacquer and cured, and then the impressions were slowly peeled off of the leaf. A microscope was used to count the number, and measure the size, of the stomata. The multiple regression test on stomata size showed evidence of latitudinal and longitudinal clines, while stomata density did not differ significantly among populations. This shows that stomata size shows genetic differences across the native common milkweed range, instead of being a plastic trait. Overall, the project can help to show that the focus of conservationists should be shifted toward using locally adapted seeds during restoration efforts.

Included in

Horticulture Commons